Generate a condition when value is false for boolean predicates

[PChambino]

I noticed that for boolean predicates the value false is being ignored. This can be counterintuitive as I would expect that name_present = false would give me all records where name equals NULL or is empty.

I found this issue #9 and implemented something starting from @cawel spec.

I am not sure if it is the best approach, but let me know what you think.

[radar]

I don't understand why we need inverse_of_true and not_true and false. These seem like really confusing predicate names. Especially when you get to inverse_of_not_true. So... not true would be false, but the inverse of that would mean true? If so, then why not use the true predicate?

[PChambino]

I agree that the implementation is confusing. The inverse_of_... predicates are simply a way to accept false values. I can try to implemented it in another way, removing the need for these strange predicates. I also accept suggestions. :)

However, the not_true and false predicates are not equivalent if you consider NULL values. For example, the true predicate will only match true values, the false predicate will only match false values, but the not_true predicate will match false and NULL values, which is the real inverse of the true predicate. But this can be an issue/request on its own.

[jonatack]

Thanks, @PChambino. I believe this issue has just been fixed yesterday, but your solution is interesting and different from the one merged in; I'll have a look at it and at your tests and see what could be merged in.

[PChambino]

Yes, #370 already fixes this issue. I still think there are some missing aspects that should be considered.

• I think it makes sense to make all "boolean" predicates (present, blank, null, not_null, true, false) behave the same way. So predicates true and false should also accept false values.
• I also think that the false predicate is not really the opposite of the true predicate (as it says in the wiki) if you consider NULL values. So predicates not_true and not_false should be added.

What do you think of this two points?

[avit]

I patched around this in our codebase by redefining not_eq and does_not_match as derived predicates.

Related: #123
Related: rails/arel#165

[PChambino]

Updated to include not_true and not_false predicates for completeness.

[jonatack]

Thanks Pedro! Could you add these predicates to the Basic Searching section in the wiki?

[PChambino]

Sure! I took a shoot at it already. Added the false predicate, changed the opposite of the true predicate to not_true, and added a short note under the false predicate. What do you think?

[jonatack]

Thanks! Seems good. I added a second sentence:

Note: the `false` predicate may be considered the opposite of the `true` predicate
if the field does not contain null values. Otherwise, use `not_false`.

Hope that is correct.

[PChambino]

In the second sentence I was actually expecting to read:

Otherwise, use not_true.

But I guess it depends on what you think "Otherwise" is referring to. What do you think about rewriting it to something like:

Otherwise, use the not_true/not_false predicates accordingly.

[jonatack]

I see. Maybe the explanation should be more explicit?